How to specify parameters for matlab's notch filter function

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Elinor Ginzburg 2020-9-16

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https://ww2.mathworks.cn/matlabcentral/answers/594457-how-to-specify-parameters-for-matlab-s-notch-filter-function

Hello,

I'm writing a code to remove specific frequency from audio file using notch filter as specified in the following documentation. I want to set the bandwidth variable to -3dB but I'm not sure how to do it (and all the examples determine the Q factor instead of the bw when Q = w/bw). The code I'm using:

[signal, fs] = audioread('signal.wav');
frequency_to_remove = 2750;
wo = frequency_to_remove/(fs/2);  
bw = wo;
[num,den] = iirnotch(wo,bw);
filtered_output = filter(num1,den1,output);

Can anyone explain me how to specify bw = -3 dB?

Thank you.